BACKGROUND: Cardiac involvement in Duchenne muscular dystrophy (DMD) is common, but usually latent without symptoms or signs in the initial period of disease. This study investigated the incidence and predictor of cardiac involvement in DMD patients. METHOD: From January 2000 to June 2005, we enrolled 45 patients with DMD (aged 20.2+/-3.0 years) who admitted to the Yongdong Severance Hospital. Electrocardiography and transthoracic echocardiography was done to evaluate the cardiac function. RESULT: Electrocardiographic abnormalities were present in 80.1% of patients. Sinus tachycardia was most common (50%). LVEF was decreased (46.7+/-13.8%), and 56% of the patients had diastolic dysfunction. Patients with pulmonary involvement were older (20.7+/-3.8 vs 17.6+/-2.8 years, p=0.028), and patients with reduced LVEF (<50%) had longer duration of disease (11.4+/-4.4 vs 14.3+/-2.4 years, p=0.04). However, on multivariate analysis, age, duration of disease, pulmonary involvement, dyspnea symptom, electrocardiographic abnormality was not an independent predictor for LV systolic dysfunction in adolescent and adult patients with DMD. CONCLUSION: Cardiac involvement in adolescent and adult patients with DMD was frequently observed independent of age, duration of disease, pulmonary involvement, and dyspnea symptom. Therefore, more active cardiac investigation is required in patients with DMD, even without clinical suspicion.